This invention relates to a method, devices and reagents for Fenton reaction-based wastewater purification.
Despite the significant advances in the search for greater efficiency and productivity of the chemical processes involved in biodegradability, the treatment of industrial effluents containing organic contaminants remains a serious problem to be solved.
There is great concern in the search for economic alternatives that permit effective degradation of the organic load and its toxicity. A particularly important alternative is chemical treatment with agents that transform organic contaminants into harmless compounds, carbon dioxide and water by means of an oxidation process.
In 1894, Fenton discovered the oxidation of organic molecules in an aqueous solution by the simultaneous addition of a water-soluble iron catalyst and hydrogen peroxide (Walling C., “Fenton's Reagent Revisited,” Accounts of Chemical Research, Vol. 8, No. 5. 125-131 (1977)).
The Fenton reaction (hydrogen peroxide in the presence of iron salts) consists of the oxidation of the organic matter contained in effluents using hydroxyl radicals resulting from the controlled decomposition of the peroxygenated water as an oxidizing agent. The iron acts as a hydrogen peroxide activator, generating hydroxyl radicals with an oxidation potential greater than that of permanganate.H2O2+Fe+2→Fe+3+OH−+HOo 
The Fenton reaction degrades the organic matter into increasingly simpler compounds until reaching the final formation of CO2 and H2O.
The global reaction is as follows:CnHm+(4n+m)/2H2O→n CO2 +(2n+m)H2O
The stoichiometric consumption of the H2O depends on the oxidation of the organic materials, which defines the chemical oxygen demand (COD). The presence of free H2O2 and chlorides in the effluent interferes with the COD analysis, which makes it advisable to use the TOC (Total Organic Carbon) as the control analysis.
Patent documents describe wastewater purification via treatment with Fenton reagent, such as, for example, European publication number EP0022525, which defines a process for decreasing the chemical oxygen demand of effluents by treating them with oxygenated water in the presence of a transition metal.
The Japanese patent with publication number JP56113400 defines a wastewater treatment that decomposes the organic matter by adding iron salts and oxygenated water and heating to 50° C.-70° C. for more than 60 minutes. It is subsequently treated, under agitation, with an anionic exchange resin that adsorbs the decomposed substances.
Document DE4314521 describes a process for continuous or discontinuous operations for purifying industrial wastewater contaminated with organic matter by means of the addition of hydrogen peroxide and a homogenous catalyst, preferably Fenton reagent. The reaction is carried out at 35° C.-40° C.
The method, devices, and purification reagents of this invention optimize the oxidation of organic contaminants in wastewater under conditions advantageous for the treatment of flows that may be elevated.